write_margin.

* src/transport.c (init_transport_connection): Initialize write_margin.
(transport_connection_kill): Renamed function. Was transport_kill.
(transport_write_almost_full): New function.
(transport_start_write): Use transport_write_almost_full.
(transport_stop_write): Likewise.
(transport_send_packet): Slight simplification, using local
variable writer.
(transport_send_kexinit): Generating
TRANSPORT_EVENT_STOP_APPLICATION, not
TRANSPORT_EVENT_START_APPLICATION.

Rev: src/transport.c:1.6.2.12
Rev: src/transport.h:1.7.2.10